1. Technical Field
This disclosure relates to an image processing method, a program, an image processing device, an image forming apparatus and an image forming system.
2. Description of the Related Art
As an image forming apparatus such as a printer, a facsimile, a copying machine, and a composite machine thereof, for example, an ink jet recording apparatus in which a liquid drop ejecting head is used for a recording head is known. An ink jet recording apparatus performs image formation (recording, character printing, image printing, and printing may be used as synonyms.) by ejecting ink as recording liquid from an ink recording head onto a paper form (which is not limited to a paper but includes an OHP sheet, etc., means an object to which an ink drop or other liquid can adhere, and may be called a medium to be recorded, a recording medium, a recording paper, or a recording paper form).
In order that such an ink jet recording apparatus spreads from a personal field to an office field, the following two main problems have to be solved. First, recording speed is provided as one problem. In a general ink jet recording apparatus except a special type for industry, a recording head which is much smaller than a recording paper form scans the paper form many times and ink drops are sprayed, thereby performs recording. This is sort of a “line” recording method and rather disadvantageous with respect to recording speed, compared to an electrophotographic image forming apparatus for performing paper form (page) unit, that is, “surface” recording.
In order to overcome the disadvantage with respect to recording speed, the improvement of scanning speed by making the frequency of jetting of ink drops be higher and the improvement of efficiency of a scanning sequence such as the reduction of the number of scanning by sizing up a recording head or performing bidirectional recording and the minimum control such that scanning is performed on only an image data recording portion have been employed. Accordingly, in regard to a small or middle number of printings, rather, recording speed higher than that of electrophotography can be realized.
As the second problem, the compatibility with normal papers is provided in regard to the cost. When a special purpose paper is used, significantly high quality imager reproduction can be made in regard to an ink jet recording image, and in a recent ink jet recording apparatus for a personal application, an image quality as if it were that of a photograph can be obtained.
However, these special purpose papers are commonly expensive and it is difficult to introduce them when a tight cost management is required in a company, etc., and since such an image quality is required for an image output for an office application, it is a large demerit to form a high quality image on only the special purpose papers.
Therefore, ink composition is improved in order to have the compatibility with normal papers, and, for example, the development of a lower-permeable dye-type ink, the utilization of a fixation adjuvant, the development of a pigment-type ink, etc., are challenged to, so that the most recent model can form an image with a quality comparable to that of an electrophotographic image forming apparatus, even for normal papers which are generally utilized in an office or paper forms which are generally utilized as a paper norm for copy.
Thus, an ink jet recording apparatus has also been a very attractive product in an office by the improvement with respect to speed and image quality. Particularly, since the advantage thereof with respect to the cost is high and miniaturization thereof is easy compared to a laser printer, the utilization on desktop also proceeds.
However, ink jet recording in which fixation is performed by utilizing the permeation of a coloring material into a paper form and which is different from a laser printer having a mechanism for fixing a coloring material on the surface of a paper form and an image forming apparatus for offset printing, etc., always has a problem or constraint involved in such a permeation process.
That is, there is provided a problem of cockling such that a paper form swells by water content contained in ink and the deformed paper contacts a recording head so as to contaminate the recording surface thereof. It is necessary to decrease the gap between a recording head and a paper form as much as possible in order to improve the precision of an ink drop jetting position. However, since an approach for the prevention of swelling, etc., is not applied to normal papers used in an office, which is different from special purpose papers, a contact of the swelled paper and the head may cause defective image output when the gap is set to be too small.
Also, problems may be caused such that undried ink dropped on the surface of a paper form contacts and pass along a member of conveyance mechanism whereby ink adhering to the member contaminates the surface of a paper form and undried ink on the surface of an ejected paper form contaminates the back surface of a subsequently ejected paper form.
Against these problems, conventionally employed are means of reducing a physical contact surface by increasing the gap (distance) between a recording hand and a paper form, of retaining a drying time by optimizing a character printing sequence or of providing a heater for forced drying, etc.
However, the increase of the gap between a recording head and a paper form is a factor of lowering the precision of a dot position. Also, as stopping is conducted to retain a drying time, the throughput is lowered. Further, the setting of a heater needs to worry about the safety as well as cost up, and in some cases, a warmed paper form may
Therefore, an approach from the viewpoint of ink formulation has been developed recently, so that recording can be performed on normal papers without the quality of character printing deteriorating if special means as described above are not necessarily used. For example, ink does not remain on the surface of a paper form but the permeation thereof is rapidly conducted, by increasing the permeability thereof into a paper form, and therefore, the secondary transference by the contact of a component and a paper form can be prevented. Due to such an improvement, an ink jet recording apparatus can realize recording speed comparable to that of a laser printer in regard to “single face recording” (single face printing).
Herein, against the limitation of “single face recording”, “double face recording” (double face printing) still requires to retain a drying time and it takes a recording time more than one at the time of “single face recording” due to this drying time. The reason why a drying time has to be retained is to prevent the secondary transference at the re-load (re-setting) of paper forms. Commonly, in a paper form conveyance mechanism, there are provided a roller-shaped component such as a pressurizing control roller or press control roller for pressurizing and sending a paper form for the purpose of preventing the floating and displacement of the paper form. When the recording surface of an undried paper form passes under the pressurizing control roller, undried ink is transferred onto the surface of the pressurizing control roller and the ink is transferred onto the surface of the paper form by the rotation of the control roller as if offset printing were made. Ink having permeated into the paper form is not re-transferred again to such a component at the level of contacting, but under the pressurizing control roller, a situation such that ink in the paper form is forcedly squeezed is provided so that the another transference easily occurs.
In order to reduce such a waiting time, a method of suppressing the quantity of used ink at the time of double face recording has been suggested. For example, it is disclosed in Japanese Patent No. 2879872 to suppress the quantity of used ink by means of thinning, etc., as well as to adjust a waiting time for drying depending on the kind of a recording paper form. This also aims to prevent the secondary transference and back face bleeding, that is, bleeding to the back side which is caused by the permeation of ink recorded on the surface on the front side and lowers the image quality of double face printing.
Also, it is disclosed in Japanese Laid-Open Patent Application No. 09-123431 to determine whether output image data are characters or not and, if they are not characters, to adjust the quantity of ejected ink so as to suppress the quantity of water adhering to a paper form.
Further, it is disclosed in Japanese Laid-Open Patent Application No. 2005-053087 to limit the quantity of adhering ink by means of γ-correction.
Furthermore, it is disclosed in Japanese Laid-Open Patent Application No. 2002-036528 to limit the quantity of adhering ink by reducing the maximum number of dots per unit surface area at the time of double face printing than one at the time of single face printing, thereby preventing the secondary transcription and the back face bleeding.
However, in regard to the methods disclosed in Japanese Patent No. 2879872, Japanese Laid-Open Patent Application No. 09-123431, and Japanese Laid-Open Patent Application No. 2005-053087 listed above, the quantity of ink adhering to a paper form can be practically limited but a problem occurs such that the density of an image is entirely lowered since the effect of the limitation influences over the entire image.
For example, in regard to an image data which only include a primary color, the quantity of adhering ink is at most that of ink used for single color and solid printing, wherein a quantity of adhering ink for the single color and solid printing is not necessarily an unusable quantity for the double face recording although it depends on image data. Nevertheless, the suppress is forcedly applied to a color phase for which the maximum color gamut can be originally retained, by performing the limitation of ejected quantity or the thinning process, and therefore, the image quality is lowered.
Also, in the method disclosed in Japanese Laid-Open Patent Application No. 2002-036528, an adhesion quantity comparable to one at the time of single face printing can be provided in regard to an image data which only include a primary color and an image quality for a low or middle tone can be comparable to one at the time of single face printing even in regard to secondary or tertiary color image data, but the continuity of tone is lost near the maximum dot numbers. Also, this method can be applied to the processing of an image composed of dots with a single diameter and a problem occurs such that it cannot be applied to the processing of an image composed of dots with plural diameters.